Grinding machine



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G. S. GOULD GRINDING MACHINE Aug. 20, 1957 ll Sheets Sheet ll lNVENTOR Filed June 29, 1953- GARDNER s. OULD mumww+ 4 ,Arr s United States Patent GRINDING MACHINE Gardner 5. Gould, Lunenburg, Mass.

Application June 29, 1953, Serial No. 364,664

9 Claims. (CI. 51-95) This invention relates to grinding machines primarily for grinding cylindrical, flat, and other surfaces.

It is the general object of the invention to provide an improved grinding machine which is capable of more rapid and accurate sustained work with reduced set-up time. In accomplishing this general objective the machine includes an improved automatically operating mechanism for feeding the wheel against the w-ork,'both with respect to rapid infeed in which the wheel approaches the work preliminary to grinding and also control of the infeed during grinding to a predetermined dimension. This feature includes improved mechanism for setting up or indexing the wheel relative to the work, mechanism for rapid changes of positions of wheel and work support for grinding various work sizes on a particular workpiece, for instance, as steps or changes of dimension in a cylindrical workpiece, improved mechanism for accurately and rigidly supporting both the work and the wheel so as to avoid inaccuracies due to vibration and play or looseness in the mechanism, and improved mechanism for truing or dressing the wheel between passes across the work and for automatic compensation of the relative position of the wheel wtih respect to the work due to reduction of wheel size in truing.

These and other features will become apparent from the following description and the drawings in which Fig. l is an end elevation partly in section.

Fig. 2 is a front elevation.

Fig. 3 is an end elevation of some of the parts taken from the end opposite that of Fig. 1.

Fig. 4 is a top plan view of part of the machine, partly in section.

Fig. 5 is a front elevation of some of the parts, partly in section.

Fig. 6 is a front elevation of the wheelhead clamp mechanism, partly in section.

Fig. 7 is a top plan of the wheel head clamp mechanism.

Fig. 8 is an end view showing the details of the wheel positioning mechanism, partly in section.

Fig. 9 is an end view in section showing further details of the mechanism of Fig. 8.

Fig. 10 is a rear view partly in section of parts of the truing tool carriage.

Fig. 11 is a detailed sectional view showing the truing tool and its associated parts.

Fig. 12 is a detailed view partly in section showing the cam follower and its parts at the bottom of thefswing frame.

Fig. 13 is a detailed view partly in section showing the means for traversing the work table on the swing frame.

Fig. 14 is a detailed view partly in section showing parts of the cross feed mechanism for the wheel head'and truing tool.

Fig. 15 is a detailed view of parts taken on lines 1515 of Fig. 14.

Fig. 16 is a detailed view of the feed cam and switch wheel and associated parts.

Fig. 17 is a schematic view of part of the fluid pressure actuating mechanism.

Fig. 18 is a schematic view of other parts of the fluid on a wheel head 5, these parts all being supported on a base 6.

As best seen in Fig. 2, the workpiece 1 is supported and rotatably driven by a head stock 11 and a tail stock 12 which are supported and adjustably clamped for workpiece length on a work table 13 carried by the swing frame 2. The head stock and tail stock may both be driven through belts 14, a long pulley 15 for accommodating various workpiece lengths, a belt 16 and a work drive motor 17 supported on a bracket 18 on the base. The pivot shaft 3 which supports the swing frame 2 is journallled in a pair of arms 21 extending upwardly from the base 6. A fixed shaft 22 extending acrms the swing frame 2 under the pivot shaft 3 forms with the latter a pair of cylindrical supporting slideways slidably mounted upon which are a pair of table brackets 23 and 24 which support the work table 13 so that the latter can be moved across the machine in order relatively to traverse the wheel across the workpiece surface during grinding. For this purpose a pair of traversing cylinders 25 and 26, seen in Figs. 2 and 13, are mounted in a bracket 31 secured to the swing frame 2. A piston rod 32 in the cylinder 25 is connected to the table bracket 23 and a piston rod 33 in the cylinder 26 is connected to the table bracket 24. Fluid pressure in the cylinder 25 moves the work table 13 to theleft as viewed in Fig. 2 while the cylinder 26 is exhausting and fluid pressure in the cylinder 26 moves the table 13 to the right while the cylinder 25 is exhausting in a manner to be further described, for the purpose of traversing the work back and forth across the face of the wheel. 1

Referring to Figs. 1 and 2, rapid infeed and slow infeed of the wheel into the work before and during grinding is accomplished by swinging the work 1 on the frame 2 around the pivot shaft 3 toward and against the wheel. This is accomplished by a feed cam 41 mounted on the base 6 and driven by a fluid pressure operated feed cam motor 42 on a shaft 43 (see also Fig. 16) with a WOIIII 44 thereon which drives the feed cam 41 through gears 45, 46 and 47, the feed cam 41 and gear 47 being mounted upon a shaft 48. Rotation of the feed cam 41 feeds the work 1 into the wheel 4 by acting against an eccentrically adjustably mounted cam follower 46 mounted in a lower extension 47 of the swing frame 2, thereby moving the swing frame 2 counterclockwise as viewed in Fig. 1 as the higher parts of the cam 41 move against the follower 46. A spring 49' attached to the swing frame 2 moves it clockwise to withdraw the work from the wheel against the low point 62 of the cam 41. The dwell or low point 62 provides a retracted position of the work with respect to the wheel, 'a rapid rise 63 provides rapid infeed and a gradually increasing high portion 64 provides the desired maximum amount of infeed necessary to remove work on a particular workpiece.

As shown in Figs. 1 and 12, the eccentricity of the camfollower roll 46 may be varied by a manual control knob 51 on a shaft 52 having a worm 53 engaging a gear 54 on a shaft 55 upon which the cam follower roll 46 is Patented Aug. 20, 1957 mounted eccentrically. The use of this adjustment will be further described.

On the opposite end of the shaft is mounted (see Figs. 2 and 16) a switch control wheel 49 having switch actuating pins 50 positioned about its periphery for actuating one or more control switches and 61 for a purpose to be described. Actuation of the switches 60 and 61 stops the feed cam drive motor 42 after a predetermined increment of movement of the feed cam 41 allowing the wheel to be trued before feed is continued, the feed cam motor 42 being restarted by the return traverse movement of the table 13 as will be further described.

Referring to Figs. 1, 3 and 4, the grinding wheel 4 and wheel head 5 are slidahly supported upon a pair of inclined cylindrical rods 71 forming an inclined slideway secured on the top of an inclined base portion 7. The support rods 71 slope down away from the Work and the purpose is to avoid vibration and play in the wheel head by reason of the fact that the force of gravity causes the wheel head to be loaded against the feed mechanism which holds and moves the wheel head and the Wheel toward and against the work.

The machine has an infeed mechanism for indexing the.

wheel relative to the work in setting up the machine. With this is combined an automatic mechanism for truing the wheel during the grinding cycle and for compensating for reduction of wheel radius by material removed in truing. The compensating mechanism moves the wheel toward the work by the amount equal to wheel reduction. This mechanism includes a truing diamond 74 on a carriage 72 which is mounted slidably toward and away from the wheel on a pair of cylindrical slide rods 73 on the wheel head 5, as best seen in Figs. 3, 5 and 10. The truing diamond 74 is slidable on its carriage 72 across the face of the wheel, as seen particularly in Figs. 4 and 5, being mounted for this purpose upon a cross slide 75 supported on rods '76 and 76a which are slidable in hollow slides 77 on the diamond carriage 72. The diamond 74 is moved across the face of the wheel by fluid pressure means, including a piston 78 attached to the slide rod 76 and which is operable in a fluid pressure cylinder '79, as best seen in Figs. 4 and 5. Therefore, the diamond 74 can. moved both against the Wheel and across its face for truing.

Mechanism is also provided, as seen in Figs. 3, 4, 5,

9 and 10, to move the diamond toward the wheel and to move the wheel toward the work an equal amount, including a belt, preferably in the form of a chain $1, the lower end of which is attached to a bracket 32 fastened on the base portion 7 and which runs over a pulley or sprocket 83 attached to the rear of the wheel head 5, and the upper end of which is attached to a chain clamp 84 in the. diamond carriage 72.

By this arrangement, the diamond moves twice as far as the wheel relative to the base, but since the wheelhead is also moving, the diamond moves toward the wheel the same distance the wheel moves relative to the base. Therefore the wheel is moved toward the workpiece a distance equal to its reduction in radius by the diamond.

The diamond carriage 72 is anchored to the wheel head 5 by a feed screw 91, seen in Figs. 4 and 14, threaded at its right-hand end into a nut 92 which is secured endwise in the diamond carriage 72 and at its other end secured endwise in a bracket 93 secured fast on the wheel. head 5. The rear end of the nut 92 has an external flattened portion 94, as seen in Figs. 14 and 10, by which it can be turned by application of a wrench. The nut 92, during operation of the machine, is clamped in place against rotation by a split portion 95 which is clamped securely around the nut 92 by a lock screw 96. \Vhen the nut 92 is thus clamped against rotation, rotation of the feed screw 91 moves the diamond carriage 72 toward the wheel, and this movement being imparted to the chain 81 also moves the Wheel toward the work as previously described.

The diamond carriage 72 and diamond can also be indexed relative to the wheel by rotation of the nut 92 by the application of a wrench to its exposed end 94. Therefore, when the machine is being set up prior to operation, the diamond is indexed relative to the wheel by loosening the lock screw 96 and rotating the nut 92, usually backing it off relative to the feed screw 91, so that the diamond 74 is in a position ready to make its first pass across the wheel. The lock screw 96 is then turned up to clamp the nut 92 in position. The wheel is then indexed with respect to the work by a hand wheel 101 operating through gears 102 and 103 to turn a splined shaft 104, shown in Figs. 3, 4 and 8. The splined shaft 104 is engaged to turn a nut 105 which is fixed endwise in the diamond carriage 72 but slidable endwise with respect to the shaft 104. The nut 105 is threaded into the chain clamp 84 on the upper end of the chain 81. The chain clamp 84 is slidable endwise of the diamond carriage 72 but keyed against rotation therein by a key 106. Rotation of the hand wheel 101 and nut 105 therefore moves the chain clamp 84 and the upper end of chain 81 in an endwise direction relative to the wheel head 5 without moving the diamond carriage 72 relative to the wheel 4. This in turn moves the wheel toward the work so that it can be indexed with respect thereto prior to the commencement of grinding.

After the machine is set up and the grinding operation commences and the wheel makes one or more passes across the face of the work, the truing diamond is then passed across the face of the work by the action of its piston 78 and cylinder 79. As seen in Fig. ll, the contour of the truing action of the diamond 74 across the face of the wheel 4 is determined by a cam 1111 which as illustrated is straight in order to cut the face of the wheel square but may be curved, convexly or concavely or in other shapes, to produce a like shape on, the face of the wheel. The cam controls a cam follower 111 on a slide 112 to which the diamond is attached and which is slidable toward and away from the face of the wheel in a slideway 113 in the diamond carriage 72. The diamond and its follower 111 are held against the face of the cam 110 by a spring 114 acting on a rod 115 secured to the cam follower 111.

After the diamond has been passed across the face of the wheel to true the Wheel, it is, while in the retracted position shown in Figs. 4 and 11', moved one step toward the wheel preparatory to a subsequent truing pass. At

, the same time the wheel is moved toward the work to compensate for its reduction in diameter, by an incremental rotation of the feed screw 91. This increment of rotation is imparted to the feed screw 91 by the action of a piston 121, seen in Fig. 15, operating in a fluid pressure cylinder 122 and acting upon a clutch arm 123 to move the latter to the left, as seen in Fig. 15, within a limit determined by the adjustment of a screw 124 on the opposite side of the piston 121. As seen in Fig. 14, the clutch arm 123 is attached to a one-way roll. clutch 125 on the feed screw 91, thereby imparting an incremental movement to the feed screw 91 when the clutch arm 123 is moved in one direction by the piston 121. The clutch arm 123 is returned to its original position by the action of a spring 126, as seen in Fig. 15, during which movement no motion is imparted to the feed screw 91. The piston 121 is also returned to its original position at this time.

In addition to the force of gravity which tends to urge the Wheel away from the work and against the feed mechanism which holds it toward the work for maintaining the wheel in an establishedposition during grinding, the wheel head 5 has a lock mechanism, indicated at 131 and as seen in Figs. 1, 6 and 7, for locking it in position on the slide rods 71. The lock mechanism 131 comprises a frame 132, to which is pivoted two pairs of clamps members 133 adapted to be closed in locking engagement against the rods 71. The clamp members are'closed by the opening action of two pairs of pistons 134 engaging the inner ends of the clamp members 133. When fluid pressure is admitted between the pistons, they open apart against the clamp members 133, closing the outer ends of the clamp members 133 against the rods 71.

Figs. 17 to 21 show the mechanism and manner of operation and control for the machine.

Fig. 17 shows schematically the fluid pressure system for reciprocating the work table 13 to traverse the work across the face of the Wheel. A fluid pressure pump 141 driven by an electric motor 142 supplies fluid under pressure alternately to the table rciprocating cylinders 25 and 26 through a conventional pilot operated fourway valve 143 through which fluid is metered by a bypass valve 144 to control the rate of traverse. The valve 143 is operated by a double solenoid four-way pilot valve 145. The position of pilot valve 145 is controlled by solenoids 146 and 147 as will be further described. Pressure to this pilot valve 145 is delivered by a pump 141 through a line 151 and exhausted back to a sump 152 through a line 153. Operating pressure to the valve 143 is delivered from the pilot valve 145 alternately through the lines 154 and 155. Fluid pressure to operate the cylinders and 26 is delivered to the valve 143 from the pump 141 through the line 156 and alternately as selected by the position of the valve 143, from the valve to the cylinders through the lines 157 and 158, one line being open to exhaust through the valve 143 and line 159 back to the sump when the other is open to pressure.

A pressure release valve 161 operated by a solenoid 162 is provided in a line 163 between the pump 141 and the sump 152 which, when opened when the solenoid- 162 is de-energized releases the pressure in the power line 156 when the table has come to rest at the end of a cycle. I

' A switch 165 is operated by an adjustably positioned cam 166 under the'table 13 when the table reaches the end of one table stroke and a switch 167 is operated by an adjustably positioned cam 168 under the table when the latter reaches the end of a stroke in the opposite direction. The switches 165 and 167 control the solenoids 146 and 147 respectively to reverse the pilot valve 145 and thereby to change the direction of reciprocation of the table 13, as will be further explained in connection with Fig. 21.

Referring to Fig. 18, the cams 166 and 168 under the table 13 also operate a pair of switches 171 and 172 which form part of the control system for the cross feed mechanism.

The hydraulic feed cam motor 42 (see also Fig. 1) is driven by fluid pressure supplied by the pump 141 through a stop-and-start valve 174 operated by a solenoid 175. Feed is controlled by a needle valve 176 in a by-pass from the supply line 177 between the pump and the control valve 174. Pressure is supplied to the motor 42 from the valve 174 through a line 178. Exhaust fluid from the motor 42 is drained to the sump 152 through a line 179. When the solenoid 175 is energized, the valve 174 is open to drive the motor 42 and thereby to feed the work toward and against the wheel.

Referring to Fig. 19, the fluid pressure mechanism for operating the pistons 134 of the wheel head clamp 131 to clamp the wheel head includes the pump 141 and a three-way fluid pressure valve 181 which is normally opened to admit pressure from the pump 141 through a line 183 to the pistons 134 and closed so as to exhaust fluid: pressure from the pistons 134 through the lines 183 and 184 to the sump 152, thereby unclamping the clamp elements 133 and freeing the wheel head when the solenoid 182 is energized.

- The fluid pressure mechanism for traversing the truing diamond across the face of the wheel and for feeding the diamond toward the wheel and the wheel toward the work to compensate for truing, is also shown in Fig. 19. It comprises a four-way valve 191 which controls presure to the diamond traversing piston 78 and cylinder 79 and also to the feed piston 121 and cylinder 122, and it is positioned to move the piston 78 in one direction by a solenoid 192 and to move the piston 78 in the opposite direction by a solenoid 193.

Pressure is admitted to the valve 191 from the pump 141 to the line 185. In one position of the valve 191, pressure passes through the line 195 and a needle valve 196 to the left side of the piston 78, as seen in Fig. 19, to move it to the right and also enters the cylinder 122 to move the feed piston 121 against the arm 123. In the other position of the valve 191, pressure enters on the right side of the piston 78 through the line 197 moving the piston back to the left. When one of the lines 195 and 197 is under pressure the other is open to exhaust back to the sump 152 through the valve 191 and the line 198.

The electric power and control systems are shown in Figs. 20 and 21. In Fig. 20, motor 142 for the fluid pressure pump 141 is connected between power lines 201 and 202 of suitable voltage through a stop-andstart switch 203. This may also be a three-phase system if desired. The switch 203 is closed in order to start the motor 142 and to energize the fluid pressure system prior to the commencement of the grinding cycle.

The wheel drive motor 8 and the work drive motor 17 are also connected across the power lines 201 and 202 through suitable control switches 9 and 19 respectively. Fig. 21 shows the electric control system for the various fluid pressure valves. The system is powered from power wires 205 and 206 of suitable control voltage.

'Prior to the commencement of the cycle and after the wheel 4 has been indexed with respect to the work, the work carrying swing frame 2 is in retracted position with the work away from the wheel and with the cam follower 46 in the low part 62 of the cam 41. The work table 13 is at one end of its traverse thereby holding closed one of the switches and 166, and also holding in a closed position one of the switches 171 and 172. A limit switch 210 is located so as to be held upon automatically by the retracted position of the swing frame 2 and allowed to close when the frame pivots under the action of the feed cam 41 to feed the work toward the wheel. A manually operated starting switch 211 is conveniently located at the front of the machine and normally in open position.

When the starting switch 211 is closed and momentarily held closed by hand, current passes from the power line 205 through the solenoid 162 across the switch 211 to the other power line 206 thus energizing the solenoid 162 and closing the relief valve 161 (see Fig. 17) thereby closing the fluid pressure, power line 156. Fluid pressure enters one of the cylinders 25 and 26 from the valve 143 depending upon which end of the traverse the table starts from. Current also flows from the line 205 through the solenoid via the normally closed switch 61 and across the starting switch 211 to the line 206 energizing the solenoid 175, thereby opening the fluid pressure valve 174, see Fig. 18, allowing fluid under pressure through the fluid line 178 to drive the feed cam drive motor 42 and the feed cam 41. The swing frame 2 pivots the work toward the wheel starting the in-feed cycle and allowing the switch 210 to close, whereupon the starting switch 211 may be released and current continuesto flow across the switch 210 and alternating through the switches 165 and 166 and the solenoids 146 and 147 to operate the valve 145, thereby to continue the reciprocation of the work table 13. The current is also maintained through the switch 210, across the solenoid 162 holding the valve 161 closed. As long as the switch 61 remains closed, current is also .maintaiued through the solenoid 175 and the switch 210 to continue the in-feed motion. As soon as one of the pins Stl (secFig. 2) strikes, the switch 61 to open it, the circuit through the solenoid 175 becomes deenergized, the valve 174 closes and in-feed stops in order to provide an opportunity during the grinding cycle to true the wheel. The work table 13 continues to traverse until it closes one or the other of the switches 171 and 172, both of which are connected in the line through the left-hand side of the solenoid 175, as shown. A selector switch 212 is arranged to connect the power line 205 to either one or both of the switches 171 and 172. Thus, depending upon the setting of the selector switch 212, the feed valve solenoid 175 remains de-energized until the circuit is closed through whichever of the switches 171 and 172 is connected to the line 205, whereupon it is again energized and. feeding continues, the wheel meanwhile having been trued during the delay in in-feed. 1

As previously described, in order to true the wheel, and to move the wheel toward the work to compensate for the amount which is removed from the wheel during truing, the wheel is fed toward the work and the diamond is traversed across the face of the wheel and then fed toward the wheel to compensate for truing. During this incremental movement of the wheel head, the clamp 131 must be released to free the wheel head from the rod 71 upon which it slides. For this purpose, the switch G ll and a switch2i3 are connected in series with the solenoid 182 between the power lines 205 and 206. The switch 213 is a limit switch which is arranged to be held automatically closed when the cross slide 75 supporting the diamond 74 on the diamond carriage 72 is in its start position. When the pins 59 on the switch wheel 45 open the switch 61 to stop the cross feed movement, they also close the switch 60, thus completing the circuit across the solenoid 182. The latter is energized to shift the valve 31 allowing the clamp members 133 on the clamp Hi to open and to free the wheel head from the slide rods 7 l. The shifting of the valve 151 when the solenoid 182 is energized by its movement, opens a switch 214 which is arranged in operative relation with respect to it. The switch 214, being connected in series with the solenoid 192 across the power lines 205 and 2&6, energizes the solenoid 19?, thereby shifting the valve 1&1. This charges the finid pressure line 395 which moves the piston 121 and the arm 1223, thereby moving the diamond toward the wheel and the wheel toward the work to compensate therefor. The charging of the fluid line 195 also moves the piston '78 to the right as viewed in Fig. 19, thereby traversing the diamond across the wheel. As the piston 73 moves to the right, the switch 213 opens, deenergizing the solenoid E82 and locking the wheel head in place. When the piston 73 reaches the end of its movement to the right, the diamond cross slide 75' closes a switch 215 which is located in operative relation with respect to it and connected in series with the solenoid 293 between the power lines 265 and 2556. This energizes the soleno c. 193 and shifts the valve 1% reversing the fiow of liquid in the lines 195 and 197 and moving the piston 73 and its cross slide back to the left to its starting position. When the piston 78 moves to the right, the switch 213 opens, thereby de-energizing the solenoid and locking the wheel head clamp 133;. However, the switch 214, which was closed by the energizing of the solenoid T 52, remains closed until the completion of the traverse of the piston 73 to the right, The switch 214 is also operatively connected to the switch 215 so that when the latter is closed, the switch 214 is opened thereby (lo-energizing the solenoid 92 and allowingthe solenoid R93 to operate to shift the valve 1%. in the home position of the piston '78 and slide 75, the switch 215 remains closed and the switch 214 remains open until the latter is closed at the commencement of a subsequent truing cycle whereupon the closing of the switch 214 opens the switch 215.

The truing cycle is completed prior to the closing of one of the switches 171 and 172 by the, further traverse movement of the work table 13. When this occurs the circuit through the solenoid is closed to energize it, opening the fluid pressure valve 174 thereby resuming the feed movement of the feed cam 41. The pins. 50 on the switch wheel 49 may be angularly spaced around 'its periphery so as to stop the feed cam 41 and to initiate the truing cycle several times during the grinding cycle, i. e. during the revolution of the cam 41.

When the grinding cycle is completed, the cam follower as drops off into the low point 62 of the cam 41 allowing the swing frame 2 to return to retracted position. This opens the switch 216 and de-energizes the solenoids 162 and 175, thus bringing the machine to a stop.

The truing cycle may also be accomplished independently of the feed cycle by the closing of a manually operated switch 216 in the circuit with the solenoid 182.

The manual control of the position of the cam follower roll 46 at the bottom of the swing frame 2 provides a fine pre-adjustment of the operative range of the feed cam 4-1 in setting up the machine for final work size. It readily operates to split tolerances within terms of tenths of thousandths of an inch, and being a light mechanism, its position in such fine terms, is more easily changed than that of the much heavier wheelhead. Also, when it is desired to grind a large number of workpieces without stopping to true the wheel, it provides a useful means of compensating for the wheel wear which occurs.

I claim:

1. In a grinding machine having a base, a work support, and a grinding wheel and in combination, means to true the wheel and to advance the wheel toward the work support to compensate for truing comprising a wheel head supporting the wheel and slidable on the base toward the work support, said wheelhead having a pulley on its rear end, a truing tool, a carriage behind the wheel supporting the truing tool and slidable on the wheel head toward the wheel, a belt passing over the pulley, said belt being connected at one end to the carriage and at its other end to the base, and means connected to the carriage operable to move the carriage toward the wheel thereby also moving the wheel head toward the work support, said machine being constructed to cause said wheel head to be urged away from said work support and against the tension of said belt.

2. In a grinding machine having a base, a work support and a grinding wheel and in combination, means to true the wheel and to advance the wheel toward the work support to compensate for truing comprising a wheel head supporting the wheel and slidable on the base toward the work support, said wheel head having a pulley on its rear end, a truing tool, a carriage behind the wheel supporting the truing tool and slidable on the wheel head toward the wheel, a belt passing over the pulley, said belt being connected at one end to the carriage and at its other end to the base, and a feed screw connected between the wheel head and the carriage operable to move the carriage toward the wheel thereby also moving the wheel head toward the work support, said machine including means to urge the wheel head away from said work support and against the tension of said belt.

3. In a grinding machine having a base, a work support, and a grinding wheel and in combination, means to true the wheel and to advance the wheel toward the work support to compensate for truing comprising a wheel head supporting the wheel and being mounted slidably on the base on an incline from the horizontal upwardly toward the work support, said wheel head having a pulley on its rear end, a truing tool, a carriage behind the wheel supporting the truing tool and slidable on the wheel head toward the wheel, a belt passing over the pulley, said belt being connected at one end to the carriage and at its other end to the base, said wheel head being urged by gravity down the incline and against the belt and the belt being thereby in constant tension, and

9 means operable to move the carriage toward the wheel thereby moving the wheel head toward the work support by an equal amount.

4. In the combination as set forth in claim 3, means to lock the wheel head to the base and means to interlock the wheel head for truing and compensating movements of the carriage and the wheel head.

5. In the combination as set forth in claim 3, a slide on the carriage supporting the truing tool and operable to move the tool across the face of the wheel.

6. In the combination as set forth in claim 5, the truing tool being axially movable in the slide toward and away from the wheel, and a cam controlling said axial movement as the tool moves across the face of the wheel to move the tool in a predetermined path across the wheel face.

7. In the combination as set forth in claim 3, means to adjust the position of the wheel head relative to the work support independently of the position of the carriage relative to the wheel head.

8. In the combination as set forth in claim 3, means 10 adjustably to move the carriage relative to the belt independently of movement of the carriage relative to the wheel head.

9. In the combination as set forth in claim 3, actuating mechanism for said means to move the carriage toward the wheel, operable to advance said carriage in predetermined increments.

References Cited in the file of this patent UNITED STATES PATENTS 344,777 Griswold June 29, 1886 517,643 Church Apr. 3, 1894 1,447,383 Hanson Mar. 6, 1923 1,666,237 Fuller Apr. 17, 1928 1,688,068 Beyer Oct. 16, 1928 1,813,503 Merryweather July 7, 1931 1,865,067 Warsow June 28, 1932 2,010,361 Harrison Aug. 6, 1935 2,099,674 Bullock et a1. Nov. 23, 1937 2,527,804 Flygare et a1. Oct. 31, 1950 

